Not Applicable
1. Field of the Invention
This invention is in the field of optical testing of the sensitivity of the eye to light, in particular, visual field evaluation.
2. Background Information
On a world-wide basis, glaucoma is one of the leading causes of blindness. Unlike cataract blindness, which is correctable with modern surgical techniques, blindness from glaucoma is permanent. The target organ of glaucoma is the optic nerve, which transmit signals of light from the retina to the brain. No known method is available for repairing, or transplanting, an injured optic nerve.
A major diagnostic problem is that visual loss from glaucoma is almost without exception painless. The patient is not aware of the ravages of glaucoma until it is too late. To compound the problem, the intraocular pressure in glaucoma is often not elevated (termed xe2x80x9clow-tensionxe2x80x9d glaucoma), and therefore reliance upon tonometry to measure the patient""s intraocular pressure frequently leads to a blatantly false sense of security. The patient is told that glaucoma is not present, when, in reality, the disease is insidiously attacking the patient""s optic nerve, causing irreversible neurological damage to the visual system.
Visual field testing is mandatory for glaucoma diagnosis and treatment. The current gold standard of measurement of optic nerve function is visual field testing, called xe2x80x9cperimetry.xe2x80x9d A problem with this technology, however, is that far too many of the examiners performing visual field testing are inadequately trained to recognize subtle patterns in the patient""s visual field indicative of glaucoma (or other neurological disease). Such misdiagnosis, which is unfortunately frequent, again gives the patient a false sense of security.
Millions upon millions of patients throughout the world have glaucoma and are completely unaware of this. The particularly sad aspect of glaucoma blindness is that it is generally preventable with proper diagnosis and treatment. The proposed invention, which incorporates the use of telemedicine for real-time feedback and for autointerpretation of visual field performance, along with a Virtual Retinal Display, will play a major role in eliminating the all-too-common errors in visual field interpretation and the unnecessary blindness which accompanies such ignorance. By making the proper diagnosis virtually instantaneously over the Internet or other telemetric vehicle, glaucoma treatment can be instituted. Millions of patients will be spared the ravages of glaucoma.
In addition to testing for glaucomatous damage to the optic nerve, visual field testing is also used to test for a variety of neurological disorders, including cerebrovascular accidents (xe2x80x9cstrokesxe2x80x9d), trauma, brain tumors, and other diseases. The proposed invention, which incorporates real-time feedback to monitor the patient""s performance, and accurate, instantaneous diagnosis available through autointerpretation on a world-wide telemetric basis, addresses a major medical need.
With the huge data base developed by a large-scale, world-wide telemedicine system, leading international experts on glaucoma and other neurological diseases can be employed to improve the accuracy of the entire system.
Investigational work has been done on the use of neural nets xe2x80x9ctrained to interpret the visual fields from an automated perimeter,xe2x80x9d as described in xe2x80x9cInterpretation of Automated Perimetry for Glaucoma by Neural Net,xe2x80x9d by Goldbaum, et al. Spenceley, et al. have also published work in the field in an article entitled, xe2x80x9cVisual Field Analysis Using Artificial Neural Networks.xe2x80x9d Brigatti, Hoffman, and Caprioli have worked with neural networks for glaucoma identification, as described in their article entitled, xe2x80x9cNeural Networks to Identify Glaucoma With Structural and Functional Measurements.xe2x80x9d These works are limited to conventional globe-like perimeter systems.
Visual field testing is mandatory for glaucoma diagnosis and treatment, as well as for confirmatory diagnosis of many neurological disorders affecting the optic pathways and the brain. Conventional visual field testing is performed utilizing a cupola-like globe, into which the patient fixates gaze during the testing process, attempting to respond to light stimuli which appear momentarily in the field of view. Major obstacles to patient friendliness are found with conventional visual field testers, and patients consider these methods of visual field analysis troublesome. More common are expressions of frustration, helplessness, boredom, claustrophobia, and, occasionally, anger.
In U.S. Pat. No. 5,864,384 and U.S. Pat. No. 5,898,474, visual fields are performed utilizing a virtual reality testing system employing goggles or other appropriate head gear to circumvent the problems associated with forcing patients to stare into a conventional globe visual field tester. These head-mounted display systems afford the patient freedom of head and body movement, thus eliminating the claustrophobia, tedium, and anxiety often associated with gazing into a stationary conventional globe. A computerized eye movement control system, which moves the stimulus presentation in response to eye movement, enhances patient freedom.
However, all currently known systems for visual field testing involve displaying an image on a physical screen of some sort, which is then viewed by the user. Drawbacks include insufficient brightness in daylight, and limited image resolution and yield.
A head-mounted Virtual Retinal Display (VRD) system is utilized to present to a patient computer-controlled and sequenced test stimuli, thus measuring the patient""s field of view (the xe2x80x9cvisual fieldxe2x80x9d) and abnormalities thereof. The virtual retinal display projects a sequentially scanned train of light pulses in such a way as to xe2x80x9cpaintxe2x80x9d an image onto the retina, much as a television raster method generates a television picture. The brain integrates the sequential signals received by the retina, to perceive the xe2x80x9cpicturexe2x80x9d as a whole, which may be updated as frequently as desired by the associated computer, to carry on the visual field test, or tests of other visual functions. A gaze sensor, which may be multi-element, is incorporated so as to allow the gaze to be detected in a small solid angular range and, within this range, the effective fixation is deemed to be maintained. The software in the associated computer provides the generation, via the virtual retinal display, of an interest-fixation icon which encourages the gaze to trace its motion within the allowed solid angle, thus avoiding fixation fatigue. The software keeps track of the location of the test point frame of reference within that solid angle of displacement, so as to provide accurate mapping of test data on the field of view presented to the retina.
A significant advantage of the present system is that it provides relief from the stress of being required to concentrate one""s gaze at a fixed location, without head movement. Freedom of movement of the head and body in this system reduces the stress and tedium of visual function testing, thereby enhancing test performance. The present invention can be used for performing quantitative visual field, and other visual function testing, on patients of ophthalmologists, optometrists, neurologists, and other medical practitioners.
Importantly, this new testing system achieves greatly increased brightness in daylight, and greatly enhanced image resolution. Also, since the head-gear can exclude light, ambient light may not be of concern, allowing visual function testing in any room, even allowing the testing of several subjects in the same room. The present invention can be employed with a neural network, or other autointerpretation system. Further, the present invention can also be employed with global network linkage via the Internet, or other suitable transmission method, for purposes of interpretation.
In addition to visual field testing, it is within the scope of this invention to provide other virtual reality, computer-driven, interactive testing capability, such as for visual acuity and color testing. The presently-described invention uses a data processing system to provide automatic interpretation of visual field and other test data received from testing apparatus in a system which can feature a virtual retinal display system. Using virtual reality and associated head-gear configuration in an interactive computerized system allows unprecedented freedom of movement of the head and body, thus minimizing or even eliminating the stress and fatigue common with conventional non-virtual reality visual field testing systems.
The combination of automatic visual field interpretation with a head-mounted virtual retinal display system is unique and novel. The use of telemedicine for centralized interpretation of visual field testing at remote locations, and interactively modulating the performance of the patient is likewise unique and novel.
Audio feedback stimuli, such as voice, or a tone or series of tones, or tactile feedback stimuli, such as a vibration, monitor the test performance in real-time. These stimuli are generated and controlled by software in an associated computer, which receives interactive feedback stimuli from the patient. The content of the software is dictated by the need to provide technically acceptable protocols, such as for examining wide and narrow fields of view, selected areas, such as the blind spot or the fovea, and measurements of thresholds for sensitivity to light intensity, or, if desired, color. Active feedback sensing alerts the system to patient loss of attention in general, or loss of fixation in particular, for notation and reiteration of test stimuli. The system is configured to allow test stimuli to be presented to one eye at a time, or to both eyes simultaneously. Individual test points are reiterated when a result is found to be inconsistent with a predetermined norm.
The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: